Enteric bacterial diseases remain a serious and frequent cause of morbidity and mortality throughout the World especially in infants and children. The most serious of these diseases due to Salmonellae and Shigellae. In developing countries, the most frequent and serious of Salmonellosis is typhoid fever caused by Salmonella typhi. The next most common cause varies: In Southeast Asia it is Salmonella paratyphi A and in most of the remaining World it is Salmonella typhimurim (group B). Enteric bacterial diseases due to Shigellae are also serious and frequent. In particular, dysentery caused by these pathogens exerts a profound effect upon future growth and development and has a morbidity and mortality in infants and children. Both may be caused by nontyphoidal Salmonella and Shigella with their peak expression in infancy and young childhood. There is indirect literature to indicate that serum IgG antibodies to the O-specific polysaccharide of the LPS of Salmonellae and Shigellae may confer protective immunity. Accordingly, in order to boost the antibody response, especially the IgG component, to S. typhi, the other Salmonellae and Shigella, conjugate vaccines have been prepared and undergoing laboratory testing. Clinical evaluation of these products is being planned.